Deep vat fermentation of beer



Dec. 10, 1968 R. E. ZINN,

DEEP VAT FERMENTATION 0F BEER Filed June 10 1965 5 Sheets-Sheet l WORTAND YEAST FEED STARTING YEAST HOLD TANK Fig.1A

TO YEAST ROOM IN VEN TOR.

Dec. 10, 1968 zm DEEP VAT FERMENTATION 0F BEER 5 Sheets-Sheet 2 FiledJune 10, 1965 Robert E. Zinn IN VEN TOR.

DEEP VAT FERMENTATION OF BEER Robert E. Zinn INVENTOR.

Dec. 10, 1968 R. E. ZINN 3,415,654

DEEP VAT FERMENTATION 0F BEER Filed June 10, 1965 5 Sheets-Sheet 5Robert E. Zinri INVENTOR.

United States Patent 8 Claims. (CI. 99-31) ABSTRACT OF THE DISCLOSURE Abeer-making process wherein a yeast and wort mixture is fermented as aliquid body having :a depth in excess of 2.0 feet, the reciprocal ratioof the open surface area to Volume of the body being at least 20.

This .application is a continuation-impart of my earlier filedapplication Ser. No. 107,356 of May 3, 1961, now abandoned.

This invention relates to an improved process for making beer, and toapparatus for carrying out the process. By the term beer is meant thevarious fermented malt beverages commonly included within that term,e.g., lager, ale, bock, porter, and stout. The fermentation of maltbeverages is similar in many respects to fermentations in general;however, the consumption of the product by humans to satisfy thirst andfor pleasure imposes unique and severe organoleptic criteria on theproduct.

Beer is now, and for many years has been typically made in amultiplicity of fermentation tanks installed within cold storagebuildings known in the brewing industry as cellars. These tanks areusually in the form of cylinders with their axes horizontal, orvertical, although they may be rectangular or of other shape; in anyevent they are spaced for circulation of cooling air around them and topermit access by the operators. The cellars are customarily constructedwith several floors to accommodate a considerable number of the tanksboth vertically and horizontally.

The tanks for cellars are always relatively shallow in verticaldimensions, ranging between 6 and 12 /2 feet in depth, with an averageof 9 feet. The beer depth in the tanks is approximately 1 /2 feet lessthan the tank depth. The tank depth is determined partly by the way inwhich the cellars are constructed, whereby a convenient distance betweenthe floors of the building is provided. It is also due to the fact thatit has never been believed possible to carry on beer fermentationsatisfactorily in tanks of considerably greater depth. Attempts made tocarry out fermentation in much deeper tanks has generally resulted inpoorer taste and uneven quality of the product, so that it wasunsuitable for consumption.

There are a number of disadvantages in the present process and apparatusfor making beer in cellars. For example, it is impossible or at leastimpractical to provide individual temperature control for the varioustanks, or to steam-sterilize them. This is of course due to the factthat the entire cellar is kept at a desired low temperature and anyaction to change the tempenature in, or to steam-sterilize, any one ormore of the tanks would upset the temperature conditions within the restof the cellar. Also, the cellar itself must be a substantial structurein order to hold the considerable weight of the filled tanks. Theoutside walls of the cellar must be insulated in order to insureeffective temperature control Within the cellar. Cork or foam glassinsulation is ordinarily used for the purpose. Outside air is forcedinto and out of the cellar; this air is treated, usually by filteringand sometimes by washing and/or sterilizing (depending upon theimpurities in the outside air), and is usually cooled, as by passing itover cooling coils. Cooling of the cellar is alternatively accomplishedby unit coolers, or by brineor ammonia-cooled pipe coils over which thetreated air is passed. It is also generally necessary to dehumidify theair in the cellars, e.g., with lithium chloride, in order to minimizerust and corrosion which would otherwise be quite damaging and wouldrequire heavy repair and upkeep expenses.

In order to obtain product uniformity and lowered labor cost per barrel,the size of fermenters relative to brew size are preferably such thatone tank should at least handle one brew. The foam generated in thefermentation process is proportional, all other factors being equal, tothe volume of the brew; i.e., the depth of foam is directly proportionalto the depth of the fermenting liquid. As previously set forth, theconventional fermentation systems, and particularly the vessels, areexpensive difficult to manage and do not conform to efiicientengineering design. If a given volume is confined to a relativelyshallow tank, the foam will be distributed over a large area whereas ifthe same volume is confined to a deep tank, the foam layer iscorrespondingly deeper and is considerably easier to skim or removeselectively as by continuous overflow. To a large extent, most of thebitter and other undesirable flavor principles in the fermenting breware concentrated in the foam together with other and more pleasantflavors. Moreover, beer taste is expedited by using deep fermenterswhich provide deep foam because the flavor character can be controlledand the degree of blandness extended beyond the limits normaly obtainedby conventional fermentation.

It has now been found, in accordance with the present invention, thatthe fermentation of beer, to produce a highly acceptable product, can becarried out advantageously without the use of cellars and in thermallyinsulated and temperature-controlled individual tanks which provide therequisite greater beer depth and thus the greater foam depth. Despitethe greater static pressure in the brew at these greater depths, thenormal course of yeast-wort fermentation can unexpectedly be achieved,although hitherto it has generally been considered impossible orundesirable. Additionally, a volume of fermenting beer confined to adeep tank has a smaller surface area exposed to air than the same volumein a shallow tank. Preferably, the reciprocal ratio of surface area tothe volume of liquid should be at least 20, and may exceed 60 or more.It will be noted that depth alone controls the surface area to volumeratio of the beer liquid.

A principal object of the present invention is therefore to provide amethod of and apparatus for deep fermentation of beer with improvedcontrol of foam removal.

It is an object of the invention to provide a process of deepfermentation where the reciprocal ratio of surface area to the volume ofliquid is at least 20. It is another object of the invention to providea deep fermentation process wherein the reciprocal ratio of surface areato volume of liquid exceeds 40.

The object of this invention is attained by providing one or more deepfermentation tanks or fermenters of sufficient size to provide a beerdepth of at least 20 feet, each tank being jacketed with suitabletemperature control means adequate to assure the desired temperatureswithin the tanks. These tanks are supplied with wort and yeast and otherconventional ingredients prepared in the usual fashion for supplying tobeer fermentation tanks. Provisions are also made for thoroughly mixingthe ingredients as fed to the fermentation tanks, and preferably alsofor circulation of the contents of such tanks during fermentation, sothat the yeast may be effectively distributed throughout the fermentingmass to provide complete uniformity, thus assisting in assuring desiredtaste characteristics of the fermented product. Each fermenter isprovided with means for selectively removing foam from the brew surface.

Suitable apparatus for carrying out the process of this invention isshown in the accompanying drawings, which are intended to beillustrative rather than limiting, and wherein FIGS. 1A1D show a sideelevation of the apparatus and FIG. 2 is a cross-sectional view of oneof the tanks, taken along line 22 of FIG. 1C. As there shown, wort andyeast feed mixture, prepared in conventional fashion, is introducedthrough line to fermentation starting tank 12 equipped with agitator 14driven by conventional drive means 16. Tank 12 is provided with jacketmeans 15, through which brine, glycol, ammonia, or othertemperature-controlling medium is circulated, this medium beingintroduced through line 17 and discharged through line 18, fortemperature adjustment and recirculation. From tank 12 the liquid isconveyed by pump 19 through valve-controlled line 20 to the fermentingtank 22 of this invention. Alternatively, the wort and yeast feedmixture may be led through valve-controlled line 24 from line 10 throughpump 19 and line 20 directly to tank 22.

Tank 22 is provided with cover 23 and is of suflicient height to permita beer depth of at least twenty feet. Accordingly, the distance from theperiphery of cover 23 to the bottom of tank 22 should be at least abouttwentytWo feet. Tank 22 is preferably provided with an agitator 26driven by conventional driving means 28 mounted at the top of the tank.Spaced around the inside of the tank are baffles 29, extending fromadjacent the top of the tank but spaced away from the bottom as shown.Jacket means 30 is provided around the outside of tank 22. This jacketmeans may surround the entire periphery of the tank (as shown for thecarbonating tank 52, described below) or may, as shown, cover only apart of the outside of the tank. The exact arrangement will depend onthe temperature conditions prevailing in the area where the tanks arelocated, on the temperature of the cooling medium supplied, on theprecise characteristics desired in the final product, and on otherfactors, as will be obvious to those skilled in the art. Brine, glycol,ammonia, or other suitable temperature regulating medium is supplied tojacket means 34) through appropriate lines 32 and is removed throughoutlet lines 34, for temperature adjustment and recirculation back tolines 32. Steam for sterilization may be introduced at any convenientplace, e.g. through valvecontrolled line 36. Additional yeast from theyeast room may be introduced through valve-controlled line 37, if and assuch additional yeast is needed.

The pump 19 should be such as to avoid damage to the yeast cellscontained in the liquid passing therethrough. Too closely-fitting partsof the pump, coupled with excessively rapid motion thereof, may resultin rupture of the cells as they pass through the vanes and other partsof the pump impeller and casing. It is therefore usually preferable toeffect the desired thorough mixing of the yeast and wort by combiningthe effect of the pumping, through pump 19, with positive mixing, as byagitator 26, during the fermentation process. This assures uniform andthorough mixing of the batch without any damage to the yeast cells, andis an important factor in providing a completely uniform beer of desiredcharacteristics.

It is to be clearly understood that this mixing which is accomplished byagitators 14, 26, 54, and 82 is such as to just keep the tank contentsmixedi.e. to prevent settling-and to insure isothermal, homogeneousconditions. All turbulence is avoided, especially in tank 22, and theliquid surface remains substantially level, without vortices. The use ofbaffles around the inside periphery of the tanks, as shown, is ofconsiderable help in avoiding vortex formation. The mixing action alsoprevents build-up of stagnant film on the sides of the tanks. Vigorousagitation adversely affects fermentation, damages yeast cells, causesexcessive frothing and loss of carbon dioxide, as well as of some otheringredients into the foam, and results in a poor-tasting product. Theagitators themselves must of course be so designed as not to damage theyeast cells.

A valve-controlled exhaust duct 38 is provided at the top of the tankfor removal of carbon dioxide as it forms during fermentation. Thiscarbon dioxide may be vented, but is preferably recovered, e.g., for usein the following carbonating tank. Process and apparatus for thusrecovering and reusing the carbon dioxide are well known.

After fermentation, the agitator 26 is stopped and the yeast allowed tosettle. This yeast is drawn off through line 39 and delivered to holdtank 40, whence it is conveyed back into the process for reuse inconventional fashion. The fermented beer is then discharged from tank 22through valve-controlled line 41 into yeast separation means 42, e.g., acentrifuge, wherein the yeast is removed and whence it is dischargedthrough line 43. Depending upon the quality of this yeast, it may bepassed to hold tank through line 44, if it is of good quality, or bedischarged from the system through line 46 if consisting mainly of deadcells. On the other hand, it is possible to remove all the yeast byseparation means 42, but that is usually less desirable, as the settlingstep serves to separate automatically the better grade of yeast from thedead cells, as the latter tend to float in the beer without settling.

Means are provided for selectively removing foam accumulating on thesurface of the fermenting liquid in tank 22. This can be accomplishedsimply by maintaining the surface of the fermenting liquid apredetermined depth beiow a discharge port such as line 38. In suchevent, because line 38 also serves to vent carbon dioxide, foamseparator 47. is provided in line 38. While this arrangement willeffectively remove foam which rises above the level of the dischargeport, because the depth of foam remaining is predetermined by thesubstantially fixed distance between the port and liquid surface, thisarrangement tends to impose sharp limitations on the total volume offermenting liquid required. Thus, alternatively, foam removal isaccomplished by providing float 33 positioned to float on the surface ofthe fermenting liquid and supporting line 31 which is flexibly connectedto conduit 35, the latter being valved to discharge to waste-line 45.The inlet to line 31 will remain at a predetermined fixed level abovethe surface of the fermenting liquid regardless of variations, withinobvious limits, of the level of the liquid in the tank.

Removal of foam through line 31 or line 38, as the case may be, asabove-noted serves to control or reduce bitter flavor principlesoccurring in some types of beer fermentation.

The present invention provides for a given volume of liquid to produce adense foam confined within a small surface area thus increasing thedepth to volume ratio of the foam and facilitating its removal withminimum disturbance to the foam-liquid interface. The foam layer can beremoved leaving a minimum residual foam that is desirable for thepurposes of retaining surface characteristics favoring entrapment ofsolids Which collect on the surfaces of rising gas bubbles, andpreventing reentry of the solids into the liquid. Hence, the deepfermenter design provides an effective foam cover at minimum foam volumeper liquid volume.

Because in making ale, the yeast is top fermenting and is removed fromthe surface of the liquid, either float 33 and line 31 can be used toeffect the latter procedure, as by including another valve arrangementwhereby line 35 can be diverted to discharge into line 39.

From the yeast separator 42 the resulting beer is conveyed throughvalve-controlled line 48 by pump 50 into carbonating tank 52 which isprovided with agitator 54, conventional driving means 56 therefor,baffles 57 (similar to those in tank 22), and jacketing means 58 whichin this instance is, for illustration, shown as surrounding the entiresides of tank 52. Temperature-controlling fluid such as brine, glycol orammonia enters through line 60 and passes out, for temperatureadjustment and recirculation, through line 61. Alternatively, thejacketing means around tank 52 may be only partial, as in the case oftank 22. Steam inlet 63 is provided, for the purpose as described withrespect to tank 22. Purified carbon dioxide which as already stated mayhave been recovered from tank 22 through line 38 is introduced into tank52 through line 62, and carbonation proceeds in the usual fashion. Gasesare exhausted through valve-controlled line 64. Tank 52 is maintained atappropriate superatmospheric pressure, e.-g., -15 p.s.i.g., and thetemperature of the contents is kept slightly above freezing, e.g., 30 to36 F.

The carbonated product is removed through valve-centrolled line 70,impelled by pump 72, whence it passes into filter 74 for removal of anysludge formed in the carbonating step, and thence throughvalve-controlled line 78 to finishing tank 80. This tank is similar inarrangement to tank 22, having agitator 82, driving means therefor 84,and jacket means 86 provided with brine or other temperature controllingfluid introduced through line -88 and removed through line 89.Alternatively, the jacket means may be as shown for tank 52. Purifiedcarbon dioxide, if desired, may be added through line 90, as is donethrough line 62 in tank 52. Steam for sterilizing may be introducedthrough valve-controlled line 91. This tank is commonly operated atabout -20 lbs. gauge pressure. It is held at a temperature close to andjust above the freezing point of the beer. This chililng actioncontributes to making the beer chill-proof by causing precipitation ofproteinaceous and other substances that might otherwise cloud thebottled product on standing in a cool place.

It should be pointed out that the critical and most important aspect ofthis invention is that relating to the fermentation tank 22 and itscharacteristics and operation, as already described, and that thesubsequent steps, after the fermentation step with foam removal, and theyeast removal, can be carried out in conventional or other fashioninstead of that here described. Nevertheless, it is highly desirablethat these subsequent steps, regardless of their order, be carried outin individual, separatelyjacketed and temperature-controlled tanks ofthe type and dimensions of tank 22 (although they may be jacketed astank 52), in order to provide the advantages herein referred to for suchtanks.

The beer product is removed from tank 80 through "valve-controlled line92 provided with pump 94, whence it passes through filter 96 whereinsubstances precipitated in tank 80 are removed. Thence the beer passesthrough line 98 to the bottling plant.

Removable covers 99 seal manholes which are provided at the top of eachof the tanks 12, 22, 52, and 80 in order to permit entrance of operatorsfor cleaning or repair purposes.

The normal action in the deep fermentation process is a faster rate offermentation than the process in shallow tanks because with theincreased depth of the liquid, a larger percentage of yeast and solidsremains suspended which in combination initiates a more vigorousfermentation that continues .at a faster rate into a higher degree ofattenuation. Consequently, because of the high degree of attenuation,the storage (aging time) can be substantially reduced. The continuousmixing provided by agitator 26 results in faster fermentation so thatthe fermenting process can be carried out in approximately less timethan without such agitation. As already pointed out, however, suchmixing is not absolutely necessary as long as provisions are made forassuring thorough mixing of the yeast throughout the entire liquid masswithin tank 22. While such mixing may be reasonably well performedthrough the action of pump 19, with increasing tank depth it isdistinctly preferable to have the mixing means within the tank, such asagitator 26. The thorough mixing assures isothermal conditions andimproves heat transfer throughout the liquid in the tank. Uniformity inthe product is thus promoted. Other arrangements of agitators may beprovided, e.g. several in large-diameter tanks. It is also possible, forexample, to provide mixing by the introduction of carbon dioxide orother suitable gas through the bottom of tank 22.

The temperature within each of the tanks is controlled according to thetype or characteristics desired in the beer product. Thus, in makinglager, the temperature ranges between 35 and F., generally around 55 F.,while in making ale, the temperature ranges between 45 and 77 F.,generally 68 F. As already pointed out, the temperature of each tank iscontrolled independently of the other tanks. It is thus possible, ifdesired, for one plant to run some of the tanks under one set ofoperating conditions and temperatures and other tanks under otherconditions, and thus simultaneously to produce two separate kinds orqualities of beer. It is also possible to change at will the temperaturecycle within any one or more tanks during processing, e.g., to startfermentation at a high temperature and then continue it at a lowertemperature.

The tanks used in practicing this invention may be of any convenientdiameter. The process works prefectly Well in tanks as little as twofeet in diameter even though as much as 40 feet deep or deeper. As apractical matter of construction, however, the depth and diameterdimensions should be fairly comparable, maintaining the reciprocal ratioof surface area to volume of liquid at least at 20. Upper limits of tanksize are imposed by practical building considerations, rather than bythe operability of the process. Thus, in a tank 70 feet deep the liquidpres sure at the bottom is about 30 p.s.i.g., and the tanks must bebuilt to resist pressure of that magnitude. Although the process of thisinvention can be carried out in such a tank, the problems ofconstruction, space, and operating usually dictate a larger number ofsomewhat shorter tanks. Similarly, this process can be carried out intanks of great diameter, e.g., 70-80 feet, but here again, structuralconsiderations usually dictate tanks of somewhat lesser diameter. In thelarger-diameter tanks more than one agitator is preferred in order toassure the desired circulation.

Stainless steel is a good material for the tank structures, or at leastfor inside cladding thereof. It is noncorrosive and provides thenecesiary strength, ease of cleaning and sterilizing, and inertnesstoward the contents.

The use of a sterilizable tank surface, e.g., stainless steel, togetherwith the fact that the tanks are individually temperature-controllable,and the provision of steam inlet means 36, 63, and 91, makes it possibleto produce a sterile beer product, if desired.

The following example, illustrative rather than limiting, will serve toprovide additional detail:

EXAMPLE I A feed of conventional formulation for making lager wascharged from the starting tank to fill a large fermenting tank having adepth of 40 feet. Temperature within the fermenting tank was initially44 /2 F. Agitator 26 was put into motion at 350 rpm. and continued for96 hours, during which fermenting took place, the foam being removed asformed. Maximum temperature during fermentation averaged 58 F., in theusual manner of programmed attemperation to favor yeast flocculence andsedimentation. The fermented product was then settled for 4 days insitu, transferred to tank 52 and there carbonated at 32-33" F. and 6-8p.s.i.g., and stored in that tank for 5 days, and finally finished for 5days in tank 80, at 30-32" F. Filtering was carried out at filters 42and 74, between each tank, and also at filter 96 following tank 80.After the latter filtration, the beer was bottled ready for use.Physical, chemical and organoleptic examinations of this product showedthat this beer was of equal, if not superior, quality to beer producedby conventional processes.

The foregoing example may be modified in various ways, e.g., byproviding a higher initial temperature, e.g., even as high as 60 F. Suchhigher temperature results in faster fermentation, but other conditionsand results are substantially unchanged.

Various modifications may be made in the conditions of operation, withinthe scope of this invention, while providing a product of good quality.For example, the initial temperature may be as high as 58 F., althoughthe average maximum is held to a fairly close range of about 5760 F.Final temperature at the end of the fermentation step in kept quite low,preferably 3335 F. The fermenting and foam removal, settling,carbonating and finished steps may take somewhat more or less time thanindicated above, ranging 4 to 5 days for each of the first two of thosesteps and 4 to 7 days for each of the last two of these steps. Beerdepth may range from 20 feet to 50 feet, or even higher. Agitation,while preferably continued for 3 or 4 days, may be for as little as anhour, or even less, although product uniformity and quality, and ease ofsettling of the yeast, are improved with the longer agitation. Othersterilizing media than steam may be used for sterilizing the tanks,e.g., beta-propyl lactone, or peracetic acid.

What is claimed is:

1. A batch process for making beer, comprising the steps of subjecting awort and yeast mixture to fermentation in the form of a liquid masshaving a depth of at least twenty feet, controlling the temperature ofsaid mass throughout a desired temperature cycle during saidfermentation, and mixing said mass to provide iso-thermic conditions andhomogeneity therein during said fermentation.

2. In a batch process for making beer, the improvement comprising thesteps of maintaining a wort and yeast mixture during fermentation in amass having a static depth of at least twenty feet, and controlling thetemperature and continuously mixing the mass to provide isothermicconditions and homogeneity therein during fermentation.

3. In a process for making beer, the improvement as defined in claim 2including the steps of continuously removing foam from the surface ofsaid mass during fermentation.

4. A batch process for making beer, comprising the steps of subjecting awort and yeast feed mixture to fermentation in a first zone, saidmixture in said first zone having a depth of at least 20 feet, mixingsaid mixture during said fermentation to provide isothermic conditionsand homogeneity therein, said mixing being effective to preventsettling, but sufficiently gentle to avoid turbulence and yeast celldamage, selectively removing foam formed on the surface of said mixtureand after completion of said fermentation, removing the yeast from theresulting fermented mixture and then moving the resulting liquid mixtureinto a second zone, there subjecting it to a carbonating step; andcontrolling the temperature of the mixture in each of said zonesindependently of the temperature of the mixture in the other zones byout-of-contact heat exchange with a heattransfer fluid.

5. A batch process for making beer, comprising the steps of subjecting awort and yeast feed mixture to fermentation in' a first zone, mixingsaid mixture during said fermentation to provide isothermic conditionsand homogeneity therein, said mixing being effective to preventsettling, but sufficiently gentle to avoid turbulence and yeast celldamage, and after completion of said fermentation, continuously removingfoam formed on the surface of the mixture during fermentation, removingthe yeast from the resulting fermented mixture and then moving theresulting liquid mixture into a second zone, there subjecting it to acarbonating step, and then moving the resulting liquid mixture into athird zone, there subjecting it to a finishing step; and controlling thetemperature of the mixture in each of said zones independently of thetemperatures of the mixtures in the other zones by out-of-contact heatexchange with a heat transfer fluid; the mixtures in each of said zoneshaving a depth of at least 20 feet.

6. A batch process for making beer, comprising the steps of subjecting awort and yeast mixture to fermentation in a fermenter tank whichconfines the mixture to a liquid mass having a reciprocal ratio ofsurface area to volume of liquid at least 20 and having a depth of atleast 20 feet removing foam during fermentation to maintain a minimumfoam cover volume to liquid volume, controlling the temperature of saidmass throughout a desired temperature cycle during said fermentation,and mixing said mass to provide isothermic conditions and homogeneitytherein and keep the yeast in suspension in the wort to substantiallythe end of said fermentation.

7. A batch process for making beer, comprising the steps of subjecting awort and yeast mixture to fermentation in the form of a liquid masshaving a reciprocal ratio of surface area to volume of liquid at least20 and having a depth of at least 20 feet, and controlling thetemperature of said mass throughout a desired temperature cycle duringsaid fermentation.

8. A process as defined in claim 7 including the step of removing foamduring fermentation to maintain a minimum foam cover volume to liquidvolume.

References Cited UNITED STATES PATENTS 12/1942 Silhavy 99228 X OTHERREFERENCES LIONEL M. SHAPIRO, Primary Examiner.

D. M. NAFF, Assistant Examiner.

U.S. Cl. X.R. 143

